A function f, defined for all positive real numbers, satisfies th…

MCQ

A function $f,$ defined for all positive real numbers, satisfies the equation $f(x^2) = x^3$ for every $x > 0$ . Then the value of $f ‘ (4) =$

A
$12$
✓
$3$
C
$3/2$
D
cannot be determined

✓

Answer

Correct option: B.

$3$

b
$2x f ‘ (x^2) = 3 x^2 ; 4 f ‘ (x) = 12 ==> f ‘ (4) = 3$

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